None-there weren't any light bulbs in the 13th century.
Two. One to hold the bulb, and another to spin the story until the bulb fits.
Two-one to shoot the old bulb out and one to screw the new one in.
They grab the stack of un-signed adoption papers, stand on top of them, then proceed to change the light bulb.
Only one; However, it takes an entire emergency ward to get it back out again.
Ayatollah you already!
Does it have to be a light bulb? I've got this neat candle holder...
